I agree, that part of the story could use a little explanation. I would say maybe in a future book but she isn't doing anymore...and I trust not the fan fiction *shutters* the evils of the interweb still haunt me...

No, it's magic. The anti magic areas in the books are created through a series of spells.

Actually, this argument makes no sense, because nobody would believe anyone who said anything about Wizards, because they would never have any proof in any way.

And, now that I think about it, I'm pretty positive there would be a spell to ward against all kinds of projectiles, and in the magical world, it's pretty easy to enchant things. So, a pair of underwear that stops bullets mid-air wouldn't be surprising in the least.

Final Solution:1. drug one identified wizard, and while he is asleep, put a pocket nuclear device in him- like joker did with an oridinary bomb in batman2. find out when the wizard is going to be in hogwart, and set timer. 2. wait.3. profit.

after the loss of hogwart wizards would take a long time to reorganize and would be easier to pick one by one. also, it would take a lot of time for their population to rebuild itself.